[time-nuts] SMD TADD-1 distribution amplifier

Chris Caudle chris at chriscaudle.org
Fri Dec 18 21:15:46 EST 2015


On Fri, December 18, 2015 6:11 pm, Charles Steinmetz wrote:
> If you're careful with what goes on inside the box you won't
> *cause* any circulating ground current.

You are going to get at least a little circulating ground current because
of power supply parasitics, and for equipment running from different power
feeds you are going to get a lot of circulating ground current.  My
understanding is that is the reason the capacitively coupled BNC
connectors were originally developed, they were used on the inputs of
telecom equipment which could have signals coming from a different
building, running on a different power transformer.  You can get up to a
couple volts of ground potential difference pretty easily.

I agree that for the typical test equipment case where all the gear is
running from the same power feed it likely should not be necessary.  But
putting the connectors on opposite sides of the PCB is still just asking
for trouble.

-- 
Chris Caudle





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